Apple Shake 4 - Manual (Page 460)

460 Chapter 16 Compositing With Layer Nodes
gTol
Controls the green color channel tolerance if the type parameter is set to Threshold (2).
If pixels between the two images are less than the tolerance value, they are considered
common.
bTol
Controls the blue color channel tolerance if the type parameter is set to Threshold (2). If
pixels between the two images are less than the tolerance value, they are considered
common.
aTol
Controls the alpha channel tolerance if the type parameter is set to Threshold (2). If
pixels between the two images are less than the tolerance value, they are considered
common.
thresholdType
Active only when the type parameter is set to Threshold (2). This sets the tolerance to
“lo” or “hi.”
• 0 = lo. Changes are made only if the difference between image1 and image2 is less
than the tolerance values you set.
• 1 = hi. Changes are made only if the difference between FG and BG is greater than
the tolerance values.
tReplace
Active when the type parameter is set to Threshold (2). Toggles whether the entire pixel
is replaced, or just the channel meeting the Tolerance criteria.
Channel and Field Controls
Opening this parameter subtree reveals two subparameters.
channels: If the type parameter is set to Channel (4), the operation applies only to
the specified channels.
field: If the type parameter is set to Field (8), the effect applies only to one field.
• 0 = even field
• 1 = odd field
invert
Inverts the selection. For example, everything beyond the specified color tolerance is
included, rather than everything below the specified color tolerance.
Copy
The Copy node copies selected channels from BG to FG (replacing the images entirely).
It is common to copy over the alpha channel. To copy channels within the same image,
use the Reorder node. SwitchMatte depends on Copy, but is a macro with MMult and
Invert placed inside of the node.